Dispersion, Workability and Mechanical Properties of Different Steel-Microfiber-Reinforced Concretes with Low Fiber Content

Steel-microfiber-reinforced concrete has been proven to be an effective type of hybrid fiber-reinforced concrete (HyFRC). The microfiber used in these concretes generally include microfilament steel (MS) fibers and synthetic fibers, such as polypropylene (PP), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN) fibers. This study aims to obtain the optimal type of steel-microfiber HyFRC, with low fiber content, which can be easily used in engineering projects without special fabrication procedures, thus achieving the concept of sustainability. Four types of HyFRC that blend steel (S) fiber with MS, PP, PVA and PAN were studied. These HyFRC were compared through a systematic experimental campaign in which the fiber dispersion, mixture workability, and concrete mechanical properties were investigated. The experimental results of the fiber dispersion and mixture workability indicate the following qualitative relationship: MS > PVA ≈ PP > PAN. For the mechanical properties of the concretes, the S-MS, and S-PVA HyFRCs generate an overall higher enhancing effect than those of the S-PP and S-PAN HyFRCs and show a positive hybridization effect for most properties. The S-MS HyFRC is superior in strength, and the S-PVA HyFRC has a significantly improved toughness. Because PVA has relatively good dispersion and workability properties, and toughness is the most important and effective mechanical property in the fiber-reinforced concrete, this study recommends that the S-PVA HyFRC is the optimal type of steel-microfiber HyFRC.